Cavity resonance in a gas or liquid medium is a universal and fundamental phenomenon found in pre-historic to modern animal sound chambers, pipe and duct shaped organs, musical instruments, industrial applications, the aeronautical industry, engines, and equipment. Today, the science to determine the resonant frequencies of a multitude of these cavities, pipes, and ducts is widely understood in science and engineering. In music, such resonances are appreciated, but in industrial, automotive, and aeronautical applications for example, acoustic resonances are frequently undesirable and can lead to failure of structures, systems and components, and noise pollution. Accordingly, control or suppression of acoustic resonance is a large field with many diverse applications. While the devices heretofore meet their respective and particular objectives, there remains a need for improved control or suppression of acoustic resonance.